Method for producing metal porous body, and plating apparatus

ABSTRACT

A method for producing a metal porous body includes the steps of: performing electrical conduction treatment on a surface of a skeleton of a sheet-like resin porous body having the skeleton with a three-dimensional network structure, to obtain a conductive resin porous body having a conductive layer; performing electroplating treatment on a surface of a skeleton of the conductive resin porous body to obtain a plated resin porous body having a metal plating layer; and performing treatment of removing at least the resin porous body from the plated resin porous body to obtain a metal porous body. In the electroplating treatment, power is supplied to a rotation shaft of a rotating electrode roller while a contact surface of a power supply brush composed of a sintered body is brought into sliding contact with the rotation shaft, with a lubricant, not containing conductive metal powder, interposed therebetween.

TECHNICAL FIELD

The present invention relates to a method for producing a metal porousbody and a plating apparatus.

This application claims priority on Japanese Patent Application No.2017-240119 filed on Dec. 15, 2017, the entire contents of which areincorporated herein by reference.

BACKGROUND ART

Conventionally, a sheet-like metal porous body having a skeleton with athree-dimensional network structure has been used for various uses suchas a filter that requires heat resistance, a battery electrode plate, acatalyst support, and a metal composite. As a method for producing themetal porous body, a method has been known in which, after the surfaceof the skeleton of a resin porous body is subjected to electricalconduction treatment, metal plating is performed by means ofelectroplating treatment and treatment of removing the resin porous bodyis performed, thereby obtaining a metal porous body (see, for example,PATENT LITERATURE 1).

In the method for producing the metal porous body described in PATENTLITERATURE 1, in performing the electroplating treatment, in order toform a metal plating layer on a single surface side or each surface sideof a sheet-like resin porous body having a skeleton surface madeconductive, electroplating treatment is repeatedly performed in aplurality of plating tanks while the resin porous body is beingsequentially fed by feeding rollers and electrode rollers that serve aspower supply cathodes outside the plating tanks. A current is sent toeach electrode roller by bringing a rotation shaft of the electroderoller and a power supply brush into sliding contact with each other(see, for example, PATENT LITERATURE 2).

CITATION LIST Patent Literature

-   PATENT LITERATURE 1: Japanese Laid-Open Patent Publication No.    2015-153648-   PATENT LITERATURE 2: Japanese Laid-Open Utility Model Publication    No. H5-97082-   PATENT LITERATURE 3: Japanese Utility Model Registration No. 3075438-   PATENT LITERATURE 4: Japanese Laid-Open Patent Publication No.    2001-157413-   PATENT LITERATURE 5: Japanese Laid-Open Patent Publication No.    2011-205816-   PATENT LITERATURE 6: Japanese Laid-Open Patent Publication No.    2001-346363-   PATENT LITERATURE 7: Japanese Laid-Open Patent Publication No.    H6-84775

SUMMARY OF INVENTION

A method for producing a metal porous body according to the presentdisclosure is a method for producing a metal porous body, including thesteps of: performing electrical conduction treatment on a surface of askeleton of a sheet-like resin porous body having the skeleton with athree-dimensional network structure, to obtain a conductive resin porousbody having a conductive layer; performing electroplating treatment on asurface of a skeleton of the conductive resin porous body to obtain aplated resin porous body having a metal plating layer; and performingtreatment of removing at least the resin porous body from the platedresin porous body to obtain a metal porous body, wherein, in theelectroplating treatment, power is supplied to a rotation shaft of arotating electrode roller while a contact surface of a power supplybrush composed of a sintered body is brought into sliding contact withthe rotation shaft with a lubricant, not containing conductive metalpowder, interposed therebetween.

A plating apparatus according to the present disclosure is a platingapparatus for performing electroplating treatment on a surface of askeleton of a conductive resin porous body obtained by forming aconductive layer on a surface of a skeleton of a sheet-like resin porousbody having the skeleton with a three-dimensional network structure, toform a metal plating layer, the plating apparatus including: a platingtank; an electrode roller having a rotatable rotation shaft andconfigured to feed the conductive resin porous body to the plating tankby rotating the rotation shaft; and a power supply brush composed of asintered body, wherein the power supply brush has a contact surface thatis brought into sliding contact with the rotation shaft of the electroderoller with a lubricant, not containing conductive metal powder,interposed therebetween.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing a metal porous body.

FIG. 2 is a schematic diagram showing a battery in which the metalporous body is used as a positive electrode plate.

FIG. 3 is a flowchart showing a method for producing a metal porous bodyaccording to an embodiment of the present invention.

FIG. 4A is an enlarged schematic view of the surface of a resin porousbody.

FIG. 4B is an enlarged schematic view of the surface of a conductiveresin porous body.

FIG. 4C is an enlarged schematic view of the surface of a plated resinporous body.

FIG. 4D is an enlarged schematic view of the surface of a metal porousbody.

FIG. 5 is a side cross-sectional view showing an example of a platingapparatus.

FIG. 6 is a plan view showing a structure for supplying power to anelectrode roller.

FIG. 7 is a cross-sectional view showing a power supply device.

FIG. 8A is a side view showing a power supply brush.

FIG. 8B is a diagram of the power supply brush as seen from the lowerside of FIG. 8A.

FIG. 9 is a schematic diagram showing a modification of the platingapparatus.

DESCRIPTION OF EMBODIMENTS Technical Problem

In the case of performing electroplating treatment on a sheet-like resinporous body as in the above-described conventional art, it is necessaryto apply a large current to each electrode roller, since the surfacearea of the resin porous body is large. Therefore, a sintered bodycontaining copper or iron as a main component is generally used for apower supply brush for supplying power to each electrode roller.

However, the surface of the power supply brush for which a sintered bodyis used is porous, thus the frictional resistance between the powersupply brush and the rotation shaft of the electrode roller increases,and jerkiness (rotational failure) easily occurs at the electrode rollerthat rotates at a low speed. When such jerkiness occurs, if the amountof plating on the resin porous body is small in the electroplatingtreatment, the plating thickness of a produced metal porous body issmall, so that the skeleton of the metal porous body may be cracked thusreducing the strength, resulting in a decrease in the quality of themetal porous body.

Therefore, the present disclosure has been made in view of suchcircumstances, and an object of the present disclosure is to provide amethod for producing a metal porous body and a plating apparatus thatcan improve the quality of the metal porous body.

Advantageous Effects of Present Disclosure

According to the present disclosure, it is possible to improve thequality of the metal porous body.

DESCRIPTION OF EMBODIMENTS OF INVENTION

First, contents of embodiments of the present invention will be listedand described.

(1) A method for producing a metal porous body according to anembodiment of the present invention is a method for producing a metalporous body, including the steps of: performing electrical conductiontreatment on a surface of a skeleton of a sheet-like resin porous bodyhaving the skeleton with a three-dimensional network structure, toobtain a conductive resin porous body having a conductive layer;performing electroplating treatment on a surface of a skeleton of theconductive resin porous body to obtain a plated resin porous body havinga metal plating layer; and performing treatment of removing at least theresin porous body from the plated resin porous body to obtain a metalporous body, wherein, in the electroplating treatment, power is suppliedto a rotation shaft of a rotating electrode roller while a contactsurface of a power supply brush composed of a sintered body is broughtinto sliding contact with the rotation shaft with a lubricant, notcontaining conductive metal powder, interposed therebetween.

In the method for producing a metal porous body, in the electroplatingtreatment, the contact surface of the power supply brush composed of asintered body is brought into sliding contact with the rotation shaft ofthe electrode roller with the lubricant interposed therebetween, andthus the frictional resistance between the power supply brush and therotation shaft of the electrode roller can be reduced. Accordingly, evenwhen the amount of plating is reduced in the electroplating treatment,occurrence of jerkiness at the rotation shaft of the electrode rollercan be inhibited. As a result, occurrence of cracking, in the metalporous body, that reduces the strength of the metal porous body can beinhibited, and thus the quality of the metal porous body can beimproved.

Generally, in the case of applying a fluid between components for thepurpose of applying electricity thereto, a method in which a conductivematerial such as metal powder is mixed into the fluid to cause the fluiditself to have electrical conductivity, is adopted. However, in the casewhere conductive metal powder is contained in a lubricant thatcorresponds to the fluid, when the lubricant is used over a long periodof time, the metal powder may be oxidized, resulting in significantdeterioration of electrical conductivity. In addition, by the metalpowder aggregating into lumps and accumulating between the contactsurface of the power supply brush and the rotation shaft of theelectrode roller, the contact area between the contact surface and therotation shaft of the electrode roller may be decreased.

On the other hand, in the above (1), since the lubricant does notcontain conductive metal powder, deterioration of electricalconductivity due to oxidization of metal powder can be prevented. Inaddition, since metal powder can be prevented from aggregating intolumps and accumulating between the contact surface of the power supplybrush and the rotation shaft of the electrode roller, a decrease in thecontact area between the contact surface and the rotation shaft of theelectrode roller can be prevented, and the contact area that is stablecan be ensured.

(2) In the electroplating treatment, heat generated in the power supplybrush is preferably dissipated to the outside by a heat dissipationmember connected to the power supply brush.

In this case, a rise in the temperature of the power supply brushcomposed of a sintered body can be effectively inhibited by the heatdissipation member, and thus corrosion of the sintered body due to arise in the temperature of the power supply brush can be inhibited.

(3) In the electroplating treatment, abrasion powder generated on thecontact surface of the power supply brush is preferably guided anddischarged to the outside by a groove formed on the contact surface.

In this case, the abrasion powder can be inhibited from aggregating intolumps and accumulating between the contact surface of the power supplybrush and the rotation shaft of the electrode roller. Thus, a decreasein the contact area between the contact surface and the rotation shaftof the electrode roller can be inhibited, and the contact area that isstable can be ensured.

(4) The groove is preferably formed so as to extend in a directioncrossing a direction tangent to the rotation shaft of the electroderoller.

In this case, the abrasion powder can be efficiently guided anddischarged to the outside by the groove, and thus the abrasion powdercan be further inhibited from aggregating into lumps and accumulatingbetween the contact surface of the power supply brush and the rotationshaft of the electrode roller.

(5) Preferably, in the electroplating treatment, the power supply brushis disposed at each of the rotation shafts provided at both axial endportions of the electrode roller, and power is supplied to each rotationshaft while the contact surface of the corresponding power supply brushis brought into sliding contact with the rotation shaft with thelubricant interposed therebetween.

In this case, when power is supplied from the power supply brush to theelectrode roller, it is possible to adjust the current density to be inan appropriate range via the power supply brush, which is disposed ateach of the rotation shafts provided at both axial end portions of theelectrode roller.

(6) In the electroplating treatment, the power supply brush ispreferably biased and pressed against the rotation shaft of theelectrode roller by a biasing member.

In this case, the contact pressure between the contact surface of thepower supply brush and the rotation shaft of the electrode roller can beincreased by the biasing member.

In addition, since the contact pressure can be increased by the biasingmember, also due to the power supply brush being composed of a sinteredbody and recesses and projections being formed on the surface of thepower supply brush, even if the lubricant not containing conductivemetal powder is used, a layer of the lubricant becomes partially thin(at a portion where each local projection of the power supply brush andthe electrode roller are in contact with each other). Thus, even withthe lubricant not containing conductive metal powder, flow of a currentcan be inhibited from being blocked. Therefore, in the above (6), moresignificant effects are achieved by using a sintered body as the powersupply brush, increasing the contact pressure between the contactsurface of the power supply brush and the rotation shaft of theelectrode roller by the biasing member, and combining the use of thelubricant not containing conductive metal powder.

(7) In the electroplating treatment, when the electrode roller isrotated, a part of an outer circumference of the rotation shaft of theelectrode roller is preferably immersed into the lubricant stored withina container that is disposed below the rotation shaft.

In this case, by rotating the electrode roller, the lubricant within thecontainer can be applied to the entirety of the outer circumference ofthe rotation shaft. Thus, with a simple configuration, the contactsurface of the power supply brush can be brought into sliding contactwith the rotation shaft of the electrode roller with the lubricantinterposed therebetween. In addition, since the container is disposedbelow the rotation shaft of the electrode roller, when abrasion powdergenerated on the contact surface of the power supply brush drops due tothe weight thereof or the like, the dropping abrasion powder can bereceived within the container. Accordingly, the abrasion powder can beeasily collected during maintenance work.

(8) A plating apparatus according to an embodiment of the presentinvention is a plating apparatus for performing electroplating treatmenton a surface of a skeleton of a conductive resin porous body obtained byforming a conductive layer on a surface of a skeleton of a sheet-likeresin porous body having the skeleton with a three-dimensional networkstructure, to form a metal plating layer, the plating apparatusincluding: a plating tank; an electrode roller having a rotatablerotation shaft and configured to feed the conductive resin porous bodyto the plating tank by rotating the rotation shaft; and a power supplybrush composed of a sintered body, wherein the power supply brush has acontact surface that is brought into sliding contact with the rotationshaft of the electrode roller with a lubricant, not containingconductive metal powder, interposed therebetween.

In the plating apparatus, in the electroplating treatment, the contactsurface of the power supply brush composed of a sintered body is broughtinto sliding contact with the rotation shaft of the electrode rollerwith the lubricant interposed therebetween, and thus the frictionalresistance between the power supply brush and the rotation shaft of theelectrode roller can be reduced. Accordingly, even when the amount ofplating is reduced in the electroplating treatment, occurrence ofjerkiness at the rotation shaft of the electrode roller can beinhibited. As a result, occurrence of cracking, in a metal porous bodyobtained after the electroplating treatment, that reduces the strengthof the metal porous body can be inhibited, and thus the quality of themetal porous body can be improved.

Generally, in the case of applying a fluid between components for thepurpose of applying electricity thereto, a method in which a conductivematerial such as metal powder is mixed into the fluid to cause the fluiditself to have electrical conductivity, is adopted. However, in the casewhere conductive metal powder is contained in a lubricant thatcorresponds to the fluid, when the lubricant is used over a long periodof time, the metal powder may be oxidized, resulting in significantdeterioration of electrical conductivity, and the metal powder mayaggregate into lumps and accumulate between the contact surface of thepower supply brush and the rotation shaft of the electrode roller,thereby decreasing the contact area between the contact surface and therotation shaft of the electrode roller.

On the other hand, in the above (8), since the lubricant does notcontain conductive metal powder, deterioration of electricalconductivity due to oxidization of metal powder can be prevented. Inaddition, since metal powder can be prevented from aggregating intolumps and accumulating between the contact surface of the power supplybrush and the rotation shaft of the electrode roller, a decrease in thecontact area between the contact surface and the rotation shaft of theelectrode roller can be prevented, and the contact area that is stablecan be ensured.

DETAILS OF EMBODIMENTS OF INVENTION

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. It should be notedthat at least parts of the embodiment described below may be combined asdesired.

<Metal Porous Body>

FIG. 1 is a schematic diagram showing a metal porous body. The metalporous body 10 has a sheet-like appearance and has a skeleton 11 forminga three-dimensional network structure. A large number of pores definedby the three-dimensional network structure are formed so as to bearranged from the surface of the metal porous body 10 to the interior ofthe metal porous body 10.

The metal porous body 10 can be used, for example, as a positiveelectrode plate 21 of a battery 20 as shown in FIG. 2. That is, as shownin FIG. 2, the battery 20 in which the metal porous body 10 according tothe present embodiment is used mainly includes the positive electrodeplate 21, a separator 22, and a negative electrode plate 23 that aredisposed within a casing 24. The positive electrode plate 21, theseparator 22, and the negative electrode plate 23 are disposed withinthe casing 24 in a state of being layered. The layered body of thepositive electrode plate 21, the separator 22, and the negativeelectrode plate 23 is held in a wound state. The positive electrodeplate 21 includes the metal porous body 10 according to the presentembodiment and an active material (not shown) with which the metalporous body 10 is filled.

<Production Process for Metal Porous Body>

FIG. 3 is a flowchart showing a method for producing the metal porousbody 10 according to an embodiment of the present invention.Hereinafter, the flow of the entirety of the method for producing themetal porous body 10 will be described with reference to FIG. 3.

First, a sheet-like resin porous body that has a three-dimensionalnetwork structure and serves as a base is prepared (step ST1). FIG. 4Ais an enlarged schematic view of the surface of a resin porous body 1serving as a base. In the resin porous body 1, a large number of poresdefined by a three-dimensional network structure are formed so as to bearranged from the surface of the resin porous body 1 to the interior ofthe resin porous body 1.

Next, electrical conduction treatment is performed on the surface of theskeleton of the resin porous body 1 (step ST2). By this step, aconductive resin porous body 3 having a conductive layer 2 formed by athin electric conductor on the surface of the skeleton of the resinporous body 1 as shown in FIG. 4B can be obtained.

Subsequently, electroplating treatment is performed on the surface ofthe skeleton of the conductive resin porous body 3 (step ST3). By thisstep, a plated resin porous body 5 having a metal plating layer 4 formedon the surface of the skeleton of the conductive resin porous body 3 asshown in FIG. 4C can be obtained.

Next, treatment of removing the resin porous body 1, which is the base,from the plated resin porous body 5 is performed (step ST4). In thisremoving treatment, the resin porous body 1 is eliminated by burning orthe like, whereby the metal porous body 10 in which only the metalplating layer 4 is left can be obtained (see FIG. 4D). Hereinafter, eachstep will be sequentially described in detail.

<Preparation of Resin Porous Body>

The sheet-like resin porous body 1 having the skeleton with thethree-dimensional network structure is prepared. Examples of thematerial of the resin porous body 1 include a resin foam, a nonwovenfabric, felt, and a woven fabric, and these materials may be combined asnecessary. In addition, the material of the resin porous body 1 is notparticularly limited, but a material that can be eliminated by burningafter the metal plating layer 4 is formed on the surface of the skeletonby the electroplating treatment is preferable.

The material of the resin porous body 1 is preferably a flexiblematerial, since a sheet-like material is particularly easily broken dueto handling thereof if the rigidity of the material is high. In thepresent embodiment, a resin foam is preferably used as the material ofthe resin porous body 1. The resin foam only needs to be porous, and aknown or commercially-available one can be used. Examples of such amaterial include foamed urethane and foamed styrene. Among them, foamedurethane is particularly preferable from the viewpoint of having a highporosity. The thickness, the porosity, and the average pore size of theresin foam are not particularly limited in the present invention, andcan be set as appropriate according to use.

The thickness of the resin foam in the present embodiment is, forexample, 1.0 mm to 2.5 mm, preferably 1.0 mm to 1.6 mm, and morepreferably 1.0 mm to 1.3 mm.

In addition, the average pore size of the resin foam in the presentembodiment is, for example, 250 μm to 500 μm, preferably 300 μm to 450μm, and more preferably 300 μm to 400 μm.

<Electrical Conduction Treatment>

Next, for performing electroplating treatment, electrical conductiontreatment is performed in advance on the surface of the skeleton of theresin porous body 1. The method for the electrical conduction treatmentis not particularly limited as long as the conductive layer 2 can beformed on the surface of the skeleton of the resin porous body 1.Examples of the material for forming the conductive layer 2 includemetals such as nickel, titanium, and stainless steel, and carbon powdersuch as graphite and amorphous carbon including carbon black, etc. Amongthem, particularly, carbon powder is preferable, and carbon black ismore preferable. The conductive layer 2 only needs to be continuouslyformed on the surface of the skeleton of the resin porous body 1. Theweight of the conductive layer 2 per unit area is not particularlylimited, and may be normally about 5 g/m² to about 15 g/m², andpreferably about 7 g/m² to about 10 g/m².

As specific examples of the electrical conduction treatment, forexample, in the case of using nickel, electroless plating treatment,sputtering treatment, and the like are preferable. In addition, in thecase of using a material such as carbon black, graphite, or a metal suchas titanium and stainless steel, treatment in which a mixture obtainedby adding a binder to fine powder of the material is applied to thesurface of the skeleton of the resin porous body 1 is preferable.

As the electroless plating treatment using nickel, for example, theresin porous body 1 may be immersed into a known electroless nickelplating bath such as a nickel sulfate aqueous solution containing sodiumhypophosphite as a reducing agent. Before the immersion into the platingbath, the resin porous body 1 may be immersed as necessary into anactivation liquid containing a very small amount of palladium ions (acleaning liquid manufactured by JAPAN KANIGEN Co., Ltd.) or the like.

As the sputtering treatment using nickel, for example, the resin porousbody 1 may be attached to a substrate holder, then a DC voltage may beapplied between the substrate holder and a target (nickel) while inertgas is being introduced, whereby ionized inert gas may be collidedagainst the nickel, and the blown nickel particles may be accumulated onthe surface of the skeleton of the resin porous body 1.

<Electroplating Treatment>

When the thickness of the metal plating layer is increased by at leastone of the above electroless plating treatment and the above sputteringtreatment, it is not necessary to perform electroplating treatment.However, from the viewpoint of productivity and cost, a method ispreferably adopted in which, as described above, first, electricalconduction treatment is performed on the resin porous body 1, and thenthe metal plating layer 4 is formed on the conductive resin porous body3 by electroplating treatment.

The electroplating treatment only needs to be performed according to anordinary method. For example, in the case of nickel plating, a known orcommercially-available one can be used as a plating bath. Examples ofthe plating bath include a Watts bath, a chlorination bath, and asulfamic acid bath. In the above electroless plating treatment orsputtering treatment, the conductive resin porous body 3 is immersedinto the plating bath, the conductive resin porous body 3 and a counterelectrode plate of a plating metal are connected to a cathode and ananode, respectively, and a DC or pulse interrupted current is appliedthereto, whereby the metal plating layer 4 can be further formed on theconductive layer 2 of the conductive resin porous body 3. The metalplating layer 4 only needs to be formed on the conductive layer 2 suchthat the conductive layer 2 is not exposed (see FIG. 4C).

FIG. 5 is a side cross-sectional view showing an example of a platingapparatus 30 that continuously performs electroplating treatment on thesheet-like conductive resin porous body 3. The plating apparatus 30 ofthe present embodiment is configured to feed the sheet-like conductiveresin porous body 3 from the left side to the right side in FIG. 5, andincludes a first plating tank 31, a second plating tank 32 disposed atthe downstream side of the first plating tank 31, and a power supplydevice 50 (see FIG. 7).

The first plating tank 31 includes a plating bath 33, a cylindricalelectrode 34 (cylindrical cathode), and an anode 35 (cylindrical anode)provided on an inner wall of a container. By the conductive resin porousbody 3 passing through the inside of the plating bath 33 along thecylindrical electrode 34, the metal plating layer 4 is formed on onesurface side (the lower surface side in FIG. 5) of the conductive resinporous body 3.

The second plating tank 32 includes a plurality of tanks 36 for formingthe metal plating layer 4 on the other surface side (the upper surfaceside in FIG. 5) of the conductive resin porous body 3. The conductiveresin porous body 3 undergoes metal plating by being sequentially fedand passing through plating baths 39 in a state of being held between aplurality of feeding rollers 37 and a plurality of electrode rollers 38,which are disposed adjacent to the respective tanks 36. In each of theplurality of tanks 36, an anode 40 is provided at the other surface sideof the conductive resin porous body 3 with the plating bath 39interposed therebetween. By supplying power to the anodes 40 androtation shafts 38 a of the electrode rollers 38 (tank-outer powersupply cathodes), the metal plating layer 4 is formed on the othersurface side of the conductive resin porous body 3.

FIG. 6 is a plan view showing a structure for supplying power to therotation shafts 38 a of the electrode roller 38. The rotation shafts 38a of the electrode roller 38 are provided at both axial end portions ofthe electrode roller 38 which rotates in contact with the sheet-likeconductive resin porous body 3. Each of the rotation shafts 38 a of eachelectrode roller 38 is supplied with power by a plurality of powersupply brushes 51 each of which is in sliding contact with the outercircumferential surface of the rotation shaft 38 a. Each power supplybrush 51 is composed of, for example, a sintered body containing copperas a main component, such that a large current can be applied to therotation shaft 38 a of the electrode roller 38. The “main component”refers to a component having a highest mass content, and impurities maybe contained as long as the advantageous effects of the presentembodiment are achieved.

Each of the rotation shafts 38 a of each electrode roller 38 is composedof a sintered body made of metal, and plating can be performed on therotation shaft 38 a from the viewpoint of prevention of corrosion. Eachpower supply brush 51 may be composed of a sintered body containing amain component other than copper, such as iron.

Each power supply brush 51 is designed to be abraded against therotation shaft 38 a of the electrode roller 38. The coefficient ofdynamic friction of each power supply brush 51 is about 0.01 to 0.40 andpreferably 0.10 to 0.30. This is because: when the coefficient ofdynamic friction is less than these ranges, it is disadvantageous incost; and when the coefficient of dynamic friction is greater than theseranges, the problem arises that the slidability is deteriorated and theamount of abrasion is increased.

FIG. 7 is a cross-sectional view showing the power supply device 50including the plurality of power supply brushes 51. The power supplydevice 50 is provided at each of both axial end portions of theelectrode roller 38. The power supply device 50 of the presentembodiment includes the plurality of (in this example, two) power supplybrushes 51, a plurality of biasing members 52 that press and bias therespective power supply brushes 51 against the outer circumferentialsurface of the rotation shaft 38 a of the electrode roller 38, and acasing 53.

The casing 53 is formed, for example, by a metal member having electricconductivity. The casing 53 of the present embodiment is formed in arectangular cross-sectional shape so as to surround the rotation shaft38 a of the electrode roller 38, and the biasing members 52 are attachedto two surfaces, that is, the upper surface and the left surface, amongfour inner surfaces of the casing 53.

Each biasing member 52 is not particularly limited as long as thebiasing member 52 presses and biases the power supply brush 51 againstthe outer circumferential surface of the rotation shaft 38 a of theelectrode roller 38. For example, each biasing member 52 of the presentembodiment is formed by a plate spring that is bent in an Scross-sectional shape. One end portion of each biasing member 52 isattached to the corresponding inner surface of the casing 53, forexample, by a fixing plate 56A and a bolt 57A, and the power supplybrush 51 is connected to the other end portion of each biasing member52, for example, by a fixing plate 56B and a bolt 57B. Accordingly,contact surfaces 51 a (described later) of the two power supply brushes51 are pressed against the outer circumferential surface of the rotationshaft 38 a of the electrode roller 38 from the upper side and the leftside in FIG. 7 by the biasing force of the corresponding biasing members52.

Each biasing member 52 is preferably formed by a metal member havingboth excellent electric conductivity and excellent heat dissipation.Each biasing member 52 of the present embodiment is formed by a metalmember obtained by tinning copper having electric conductivity andhaving excellent heat dissipation. In addition, in the presentembodiment, the fixing plates 56A and 56B also have heat dissipation.Thus, the biasing member 52 and the fixing plates 56A and 56B serve as aheat dissipation member that dissipates heat generated in the powersupply brush 51 connected to this biasing member 52, to the outside. Theheat dissipation member connected to the power supply brush 51 may beformed by a member other than the biasing member 52 and the fixingplates 56A and 56B, or may be formed by the biasing member 52, thefixing plates 56A and 56B, and the casing 53.

In each power supply brush 51, a surface that faces the outercircumferential surface of the rotation shaft 38 a of the electroderoller 38 is the contact surface 51 a that is in sliding contact withthe outer circumferential surface. The contact surface 51 a is formed ina circular arc shape along the outer circumferential surface of therotation shaft 38 a of the electrode roller 38. In addition, a lubricant58 not containing conductive metal powder is applied to the contactsurface 51 a.

As the lubricant 58, a lubricating oil that is a liquid, or grease isused. In the present embodiment, liquid paraffin, which is a lubricatingoil, is used as the lubricant 58. Here, paraffin is a type ofhydrocarbon compound (organic compound), is a generic term for alkaneshaving 20 or more carbon atoms (chain saturated hydrocarbons having thegeneral formula of C_(n)H_(2n+2)), and is considered synonymous foraliphatic saturated hydrocarbons C_(n)H_(2n+2) in some cases regardlessof the number of carbon atoms. In addition, paraffin is a mixture ofhydrocarbons obtained from petroleum or crude oil through processes suchas distillation and refinement and is a colorless and transparentliquid. Liquid paraffin can be considered as a pure hydrocarbon sinceliquid paraffin is highly purified by removing impurities such asaromatic hydrocarbons and sulfur compounds contained in lube-oildistillate of petroleum that is a raw material.

In the present invention, the liquid paraffin is a mixture(weight-average molecular weight: 483) of hydrocarbons (the number ofcarbon atoms is about 15 to 20), and a reagent having a purity of about95% equivalent to first class grade is preferably used. In addition, thedensity of the liquid paraffin is preferably not less than 0.855 g/ml,and is, for example, 0.87 g/ml in the present embodiment.

When a low viscosity is defined as being 40 cSt to 75 cSt, anintermediate viscosity is defined as being 75 cSt to 300 cSt, and a highviscosity is defined as being not less than 300 cSt, the viscosity ofthe liquid paraffin is preferably the low viscosity to the lower limitof the intermediate viscosity from the viewpoint of easy handling. Inthe present embodiment, the viscosity of the liquid paraffin is, forexample, 75.8 cSt, and the kinetic viscosity of the liquid paraffin is,for example, 67.65 cSt (mm²/s at 40° C.).

The lubricant 58 is stored within a container 59 that is disposed on thelower surface within the casing 53 and below the rotation shaft 38 a ofthe electrode roller 38. An opening 59 a is formed at the upper side ofthe container 59. A part of the outer circumference of the rotationshaft 38 a of the electrode roller 38 is immersed in the lubricant 58within the container 59 through the opening 59 a. Accordingly, byrotating the electrode roller 38, the lubricant 58 within the container59 is applied to the entirety of the outer circumferential surface ofthe rotation shaft 38 a. Thus, each power supply brush 51 can supplypower to the rotation shaft 38 a by bringing the contact surface 51 a ofthe power supply brush 51 into sliding contact with the outercircumferential surface of the rotation shaft 38 a with the lubricant 58interposed therebetween. In addition, when abrasion powder generated onthe contact surface 51 a of each power supply brush 51 drops due to theweight thereof or the like, the dropping abrasion powder can be receivedwithin the container 59 through the opening 59 a.

FIG. 8A is a side view showing the power supply brush 51. In addition,FIG. 8B is a diagram of the power supply brush 51 as seen from the lowerside in FIG. 8A. As shown in FIG. 8A and FIG. 8B, a plurality of (inthis example, three) slit-shaped grooves 55 are formed on the contactsurface 51 a of the power supply brush 51. These grooves 55 are formedon the contact surface 51 a at regular intervals in the longitudinaldirection of the contact surface 51 a (the right-left direction in FIG.8A and FIG. 8B).

Each groove 55 is formed so as to extend in a direction crossing atangent direction T (see FIG. 8B) in which the contact surface 51 a ofthe power supply brush 51 is tangent to the rotation shaft 38 a of theelectrode roller 38. In the present embodiment, each groove 55 is formedso as to extend linearly over the entirety of the contact surface 51 ain the lateral direction of the contact surface 51 a (the up-downdirection in FIG. 8A and FIG. 8B) in a state of being inclined at apredetermined angle (for example, 30°) relative to the lateraldirection. Accordingly, abrasion powder generated on the contact surface51 a of the power supply brush 51 due to sliding contact with therotation shaft 38 a of the electrode roller 38 can be efficiently guidedand discharged to the outside by the plurality of grooves 55.

The current density during supply of power from each power supply brush51 to the rotation shaft 38 a of the electrode roller 38 (the ratio ofthe current to the total cross-sectional area of the power supply brush51) is about 5 A/cm² to about 15 A/cm² and preferably 8 A/cm² to 13A/cm². When the current density is less than these ranges, the size ofthe entire power supply device 50 is increased and the distance from thepower supply device 50 to the corresponding tank 36 is lengthened, andthus voltage loss is increased. On the other hand, when the currentdensity is greater than these ranges, the temperature of the powersupply brush 51 rises, and thus it is necessary to ensure heatresistance of members around the power supply brush 51, which isdisadvantageous in cost.

The weight of the metal plating layer 4 per unit area is notparticularly limited, but is normally about 150 g/m² to about 400 g/m²,and the sum of the weight of the conductive layer 2 per unit area andthe weight of the metal plating layer 4 per unit area is preferably notless than 200 g/m² and not greater than 350 g/m². This is because: whenthe above sum is less than this range, the strength of the metal porousbody may be reduced; and when the above sum is greater than this range,the power supply brush made of carbon has increased heat generation, orthe amount of plating is increased, which is disadvantageous in cost.

The electroplating treatment is not limited to the electroplatingtreatment of the present embodiment, and, for example, a platingtreatment method using a preliminary plating tank or a plating treatmentmethod using a preliminary plating tank and a lift type main platingtank may be adopted.

FIG. 9 is a schematic diagram showing a modification of the platingapparatus 30. In the present modification, the plating apparatus 30includes a preliminary plating tank 61 and a lift type main plating tank62 disposed at the downstream side of the preliminary plating tank 61.

The preliminary plating tank 61 includes a plating bath 63, an anode 64(cylindrical anode), a presser roller 65, and an electrode roller 66having a rotation shaft 66 a (power supply cathode) at each end portionthereof. The conductive resin porous body 3 preliminarily undergoesplating on one side surface (the upper surface side in FIG. 9) of theconductive resin porous body 3 by being sequentially fed and passingthrough the inside of the plating bath 63 in a state of being heldbetween the presser roller 65 and the electrode roller 66,

The main plating tank 62 includes a plating bath 67, a first presserroller 68, a first electrode roller 69 having a rotation shaft 69 a(power supply cathode) at each end portion thereof, a pair of firstanodes 70 (cylindrical anodes), a first feeding roller 71, a secondfeeding roller 72, a pair of second anodes 73 (cylindrical anodes), asecond presser roller 74, and a second electrode roller 75 having arotation shaft 75 a (power supply cathode) at each end portion thereof.

In the main plating tank 62, the conductive resin porous body 3 issequentially drawn in between the pair of first anodes 70 within theplating bath 67 in a state of being held between the first presserroller 68 and the first electrode roller 69. At this time, plating isperformed on both surface sides of the conductive resin porous body 3 bysupplying power to the rotation shafts 69 a of the first electroderoller 69 and the pair of first anodes 70.

Next, the conductive resin porous body 3 is sequentially fed between thepair of second anodes 73 by the first and second feeding rollers 71 and72 within the plating bath 67. Then, the conductive resin porous body 3is sequentially lifted from the inside of the plating bath 67 in a stateof being held between the second presser roller 74 and the secondelectrode roller 75. At this time, plating is performed on both surfacesides of the conductive resin porous body 3 by supplying power to thepair of second anodes 73 and the rotation shafts 75 a of the secondelectrode roller 75.

The rotation shafts 66 a of the electrode roller 66 of the preliminaryplating tank 61 are supplied with power by power supply brushes (notshown) that are in sliding contact with the rotation shafts 66 a.Similarly, the rotation shafts 69 a and 75 a of the first and secondelectrode rollers 69 and 75 of the main plating tank 62 are suppliedwith power by power supply brushes (not shown) that are in slidingcontact with the rotation shafts 69 a and the rotation shafts 75 a.

The power supply brushes that supply power to the rotation shafts 66 a,69 a, and 75 a of the respective electrode rollers 66, 69, and 75 areformed similar to the above embodiment, and thus the description thereofis omitted.

<Treatment of Removing Resin Porous Body>

Treatment of removing the resin porous body 1 from the plated resinporous body 5 (see FIG. 4C) obtained by the electroplating treatment isperformed. In this removing treatment, for example, the resin porousbody 1 is removed from the plated resin porous body 5 in an acidicatmosphere such as atmospheric air at not lower than about 600° C. andnot higher than 800° C. and preferably not lower than 600° C. and nothigher than 700° C., and then heating is performed in a reductiveatmosphere at 750° C. or higher (higher temperatures are desirable butthe temperature is preferably 1000° C., since higher temperatures aredisadvantageous in cost, or from the viewpoint of the material of thebody of a reducing furnace). As reductive gas, hydrogen gas or a mixedgas of hydrogen and carbon dioxide or an inert gas can be used, or thesegases can be also used in combination as necessary. In particular, it ispreferred if hydrogen gas is always added to reductive gas, since theefficiency of redox is improved.

With the method for producing a metal porous body according to thepresent embodiment and the plating apparatus 30, in the electroplatingtreatment, the contact surface 51 a of each power supply brush 51, whichis composed of a sintered body, is brought into sliding contact with therotation shaft 38 a of the electrode roller 38 with the lubricant 58interposed therebetween, and thus the frictional resistance between thepower supply brush 51 and the rotation shaft 38 a of the electroderoller 38 can be reduced. Accordingly, even when the amount of platingis reduced in the electroplating treatment, occurrence of jerkiness atthe rotation shafts 38 a of the electrode rollers 38 can be inhibited.As a result, occurrence of cracking, in the metal porous body 10, thatreduces the strength of the metal porous body 10 can be inhibited, andthus the quality of the metal porous body 10 can be improved.

Generally, in the case of applying a fluid between components for thepurpose of applying electricity thereto, a method in which a conductivematerial such as metal powder is mixed into the fluid to cause the fluiditself to have electrical conductivity, is adopted. However, in the casewhere conductive metal powder is contained in a lubricant thatcorresponds to the fluid, when the lubricant is used over a long periodof time, the metal powder may be oxidized, resulting in significantdeterioration of electrical conductivity, and the metal powder mayaggregate into lumps and accumulate between the contact surface 51 a ofthe power supply brush 51 and the rotation shaft 38 a of the electroderoller 38, thereby decreasing the contact area between the contactsurface 51 a and the rotation shaft 38 a of the electrode roller 38.

On the other hand, in the present embodiment, since the lubricant 58does not contain conductive metal powder, deterioration of electricalconductivity due to oxidization of metal powder can be prevented. Inaddition, since metal powder can be prevented from aggregating intolumps and accumulating between the contact surface 51 a of the powersupply brush 51 and the rotation shaft 38 a of the electrode roller 38,a decrease in the contact area between the contact surface 51 a and therotation shaft 38 a of the electrode roller 38 can be prevented, and thecontact area that is stable can be ensured.

In the electroplating treatment, heat generated in each power supplybrush 51 can be dissipated to the outside by the biasing member 52 andthe fixing plates 56A and 56B connected to the power supply brush 51.Accordingly, a rise in the temperature of the power supply brush 51composed of a sintered body can be effectively inhibited, and thuscorrosion of the sintered body due to a rise in the temperature of thepower supply brush 51 can be inhibited.

In the electroplating treatment, abrasion powder generated on thecontact surface 51 a of each power supply brush 51 can be guided anddischarged to the outside by the grooves 55 formed on the contactsurface 51 a. Accordingly, the abrasion powder can be inhibited fromaggregating into lumps and accumulating between the contact surface 51 aof the power supply brush 51 and the rotation shaft 38 a of theelectrode roller 38. Thus, a decrease in the contact area between thecontact surface 51 a and the rotation shaft 38 a of the electrode roller38 can be inhibited, and the contact area that is stable can be ensured.

Since each groove 55 is formed so as to extend in the direction crossingthe tangent direction T in which the contact surface 51 a of the powersupply brush 51 is tangent to the rotation shaft 38 a of the electroderoller 38, the abrasion powder can be efficiently guided and dischargedto the outside by the groove 55. Accordingly, the abrasion powder can befurther inhibited from aggregating into lumps and accumulating betweenthe contact surface 51 a of the power supply brush 51 and the rotationshaft 38 a of the electrode roller 38.

The power supply brushes 51 are disposed at the respective rotationshafts 38 a provided at both axial end portions of the electrode roller38, and power is supplied to each rotation shaft 38 a, in theelectroplating treatment, while the contact surfaces 51 a of thecorresponding power supply brushes 51 are brought into sliding contactwith the rotation shaft 38 a with the lubricant 58 interposedtherebetween. Accordingly, at the time of supply of power, it ispossible to adjust the current density to be in an appropriate range viathe power supply brushes 51, which are disposed at the respectiverotation shafts 38 a provided at both axial end portions of theelectrode roller 38.

In the electroplating treatment, since each power supply brush 51 isbiased and pressed against the rotation shaft 38 a of the electroderoller 38 by the biasing member 52, the contact pressure between thecontact surface 51 a of the power supply brush 51 and the rotation shaft38 a of the electrode roller 38 can be increased.

In addition, since the contact pressure can be increased by the biasingmember 52, also due to each power supply brush 51 being composed of asintered body and recesses and projections being formed on the surfaceof the power supply brush 51, even if the lubricant 58 not containingconductive metal powder is used, a layer of the lubricant 58 becomespartially thin (at a portion where each local projection of the powersupply brush 51 and the electrode roller 38 are in contact with eachother). Thus, even with the lubricant 58 not containing conductive metalpowder, flow of a current can be inhibited from being blocked.Therefore, in the present embodiment, more significant effects areachieved by using a sintered body as each power supply brush, increasingthe contact pressure between the contact surface of the power supplybrush 51 and the rotation shaft 38 a of the electrode roller 38 by thebiasing member 52, and combining the use of the lubricant 58 notcontaining conductive metal powder.

By rotating each electrode roller 38, the lubricant 58 within thecontainer 59 can be applied to the entirety of the outer circumferentialsurface of the rotation shaft 38 a. Thus, with a simple configuration,the contact surface 51 a of each power supply brush 51 can be broughtinto sliding contact with the rotation shaft 38 a of the electroderoller 38 with the lubricant 58 interposed therebetween. In addition,since the container 59 is disposed below the rotation shaft 38 a of theelectrode roller 38, when abrasion powder generated on the contactsurface 51 a of the power supply brush 51 drops due to the weightthereof or the like, the dropping abrasion powder can be received withinthe container 59 through the opening 59 a. Accordingly, the abrasionpowder can be easily collected during maintenance work.

[Others]

Although the method for producing a metal porous body according to theabove embodiment has been described for the case of application to amethod for producing a metal porous body that is used as an electrode ofa battery, the use of the metal porous body is not necessarily limitedto an electrode of a battery, and the method may be applied to a methodfor producing a metal porous body that is used as a filter, a catalystsupport, a metal composite, or the like that requires heat resistance.However, it is particularly effective to apply the method for producinga metal porous body according to the above embodiment to a method forproducing a metal porous body that is used as an electrode of a battery.

It should be noted that the embodiments disclosed herein are to beconsidered in all respects as illustrative and not restrictive. Thescope of the present invention is defined by the scope of the claimsrather than by the meaning described above, and all changes which comewithin the meaning and range of equivalency of the claims are thereforeintended to be embraced therein.

REFERENCE SIGNS LIST

-   -   1 resin porous body    -   2 conductive layer    -   3 conductive resin porous body    -   4 metal plating layer    -   5 plated resin porous body    -   10 metal porous body    -   11 skeleton    -   20 battery    -   21 positive electrode plate    -   22 separator    -   23 negative electrode plate    -   24 casing    -   30 plating apparatus    -   31 first plating tank    -   32 second plating tank    -   33 plating bath    -   34 cylindrical electrode    -   35 anode    -   36 tank    -   37 feeding roller    -   38 electrode roller    -   38 a rotation shaft    -   39 plating bath    -   40 anode    -   50 power supply device    -   51 power supply brush    -   51 a contact surface    -   52 biasing member (heat dissipation member)    -   53 casing    -   55 groove    -   56A, 56B fixing plate (heat dissipation member)    -   57A, 57B bolt    -   58 lubricant    -   59 container    -   59 a opening    -   61 preliminary plating tank    -   62 main plating tank    -   63 plating bath    -   64 anode    -   65 presser roller    -   66 electrode roller    -   66 a rotation shaft    -   67 plating bath    -   68 first presser roller    -   69 first electrode roller    -   69 a rotation shaft    -   70 first anode    -   71 first feeding roller    -   72 second feeding roller    -   73 second anode    -   74 second presser roller    -   75 second electrode roller    -   75 a rotation shaft    -   T tangent direction

The invention claimed is:
 1. A method for producing a metal porous body,comprising the steps of: performing electrical conduction treatment on asurface of a skeleton of a sheet-like resin porous body having theskeleton with a three-dimensional network structure, to obtain aconductive resin porous body having a conductive layer; performingelectroplating treatment on a surface of a skeleton of the conductiveresin porous body to obtain a plated resin porous body having a metalplating layer; and performing treatment of removing at least the resinporous body from the plated resin porous body to obtain a metal porousbody, wherein in the electroplating treatment, power is supplied to arotation shaft of a rotating electrode roller while a porous contactsurface of each of a plurality of power supply brushes is brought intosliding contact with the rotation shaft with a lubricant, not containingconductive metal powder, interposed therebetween, and when the electroderoller is rotated, a part of an outer circumference of the rotationshaft of the electrode roller is immersed, through an upper opening of acontainer, into the lubricant stored within the container that isdisposed on a lower surface within a casing surrounding the rotationshaft and below the rotation shaft and the porous contact surface of allthe plurality of power supply brushes.
 2. The method for producing ametal porous body according to claim 1, wherein, in the electroplatingtreatment, heat generated in the plurality of power supply brushes isdissipated to the outside by a heat dissipation member connected to theplurality of power supply brushes.
 3. The method for producing a metalporous body according to claim 1, wherein, in the electroplatingtreatment, abrasion powder generated on the porous contact surface ofthe plurality of power supply brushes is guided and discharged to theoutside by a groove formed on the porous contact surface.
 4. The methodfor producing a metal porous body according to claim 3, wherein thegroove is formed so as to extend in a direction crossing a directiontangent to the rotation shaft of the electrode roller.
 5. The method forproducing a metal porous body according to claim 1, wherein, in theelectroplating treatment, the plurality of power supply brushes aredisposed at each of the rotation shafts provided at both axial endportions of the electrode roller, and power is supplied to each rotationshaft while the porous contact surface of the corresponding power supplybrush is brought into sliding contact with the rotation shaft with thelubricant interposed therebetween.
 6. The method for producing a metalporous body according to claim 1, wherein, in the electroplatingtreatment, the plurality of power supply brushes are biased and pressedagainst the rotation shaft of the electrode roller by a biasing member.